A normal, healthy bone typically has complex surface geometry which is dictated by the function of the bone in the body. The surface of a bone rarely forms a regular geometric shape, such as a plane, cylinder, cone, or sphere. This phenomenon is exacerbated in diseased, damaged, or deformed bones. Even when a portion of a bone is removed, or resected, the cut surface may be irregular. When a bone is fractured, the potential for irregular fragments is high. Similar surfaces on adjacent bones may be a different shape and size, and are often not precisely aligned. For all these reasons, it can be challenging to fit a bone plate to bone surfaces securely enough to stabilize a developing fusion mass. This is especially true if the bone plate is designed as a regular geometric shape, such as a rectangular solid. The present invention provides an apparatus that automatically adjusts itself to fit congruently on irregular bone surfaces.
Bone plates are often secured to bone with screws, pegs, or other fixation elements. A common characteristic of these fixation elements is that they invasively penetrate the surface of the bone in order to achieve fixation. When removed, or revised, they leave behind defects which may limit the surgical options for subsequent procedures. These types of fixation elements usually rely at least in part on cancellous bone for their fixation strength. However, cancellous bone is notoriously variable in quality. Cortical bone is a superior load bearing material compared to cancellous bone. However, in many locations on the skeleton, cortical bone is distributed in a relatively thin layer. Furthermore, precisely because cortical bone is a strong load bearing material, it can be difficult to seat a cortical fixation element unless the fixation element is aligned with the cortical surface. The present invention provides an apparatus that achieves fixation in cortical bone without collateral damage to cortical or cancellous bone.